X-ray inspection systems have generally been used to inspect the contents of automobiles, trucks, rail cars, cargo containers, and other vessels of transport. Such systems are generally set up at airports, seaports, building entrances, border crossings, and other places where contraband; weapons, explosives, drugs, or other illegal items are likely to be found in transit. X-ray inspection systems are also often used to verify the contents of containers and vehicles, and to ensure the accuracy of shipping manifests and the like.
X-ray inspection systems for inspecting large objects are generally of the “fixed-site” variety, wherein vehicles or containers are brought to the inspection site to undergo X-ray imaging. Such systems commonly comprise a large inspection tunnel through which vehicles or containers are transported. The vehicles or containers are generally towed through the inspection tunnel, or are transported through the tunnel along a large conveyor mechanism.
As a vehicle or container is transported through the inspection tunnel, an X-ray imaging source generates an X-ray beam toward the vehicle or container. After the X-ray beam passes through, or penetrates, the vehicle or container, a detector receives the beam and produces an output signal representative of the vehicle or container, and of the contents located therein.
In many of these fixed site systems, a plurality of signals representative of individual segments, i.e., successive cross sections or “slices,” of the vehicle or container may be transmitted, then summed together, to represent the entire vehicle or container. The output signal, or signals, is then converted into a visual image of the vehicle or container, and of the contents located. therein, which is sent to a monitor or viewing screen so that the image may be viewed by an inspection system operator. The system operator may then determine whether any improper items are located, inside the vehicle or container, and whether the vehicle or container should be detained for physical inspection.
While fixed-site X-ray inspection systems have adequately performed in their particular implementations, the need has arisen for an X-ray imaging system that is readily relocatable and/or transportable to meet the needs of a given site or event. This is especially true given the threat that terrorism presents throughout the world, which has led to a greater need to inspect vehicles, containers, and other objects that may be carrying contraband, explosives, or other dangerous or illegal items, in a variety of settings and venues.
Current fixed-site X-ray inspection systems are not suited to meet this need, as they are unable to accommodate areas and events that are not located at, or do not take place near, the inspection sites themselves. Moreover, current fixed-site X-ray inspection systems are unable to deter a large percentage of smugglers who simply move to alternate ports of entry to avoid sites that. utilize the fixed-site inspection systems.
In an attempt to resolve these problems, relocatable inspection systems have been developed that can be assembled and used at a variety of locations to inspect large commercial vehicles and cargo containers. In use, these systems may either be stationary, similar to the fixed-site systems described above, or they may move relative to the vehicle or container to be imaged while the vehicle or container remains stationary. In the case of moving inspection systems, existing systems are generally very large and are commonly powered by internal combustion engines. These moving systems may also include linear optical encoders to measure deflection and to compensate for image distortion that occurs while the large system moves over the object to be imaged.
While existing relocatable X-ray inspection systems have been somewhat effective at inspecting vehicles and containers at multiple locations, they have many shortcomings. Specifically, they are generally extremely cumbersome to transport from one location to the next, and they require lengthy disassembling and assembling procedures. Furthermore, these systems generally require powerful machinery to load and unload their components onto and off of multiple transport trucks for relocation. Thus, significant time and expense are required to transport and assemble existing relocatable X-ray imaging systems. As a result, for a given site or event requiring such an inspection system, substantial notice must be given to allow for the time and preparation required to transport and assemble the system. This, in turn, presents significant logistical problems where an event requiring security inspections occurs on short notice.
In light of the above, a need exists for an X-ray imaging system that is used to inspect large trucks and cargo containers, which is readily relocatable, and flexible in terms of on-the-spot reconfiguration, such that a wide variety of site requirements may be met in a short amount of time, and at minimal expense.